This invention relates to a knuckle joint device, particularly to that type of adjustable knuckle joint device adaptable to being used for folding ladders with a first coupling member movably connected to a second coupling member and controlled by a snap catch positioning mechanism so that complete security, convenient operation and reduced manufacturing cost are achieved therewith.
As shown in FIG. 1, numerous conventional folding ladders are in use at the present time for various working conditions. However, so far as the applicant knows, the knuckle joints provided for these folding ladders are not really satisfactory for all users because of problems suffered by these known knuckle joints, some of which are as follows:
(1) the structure is usually complicated with too many check portions and link-up moving elements, not only causing difficulty in operation but also causing increased costs in manufacturing;
(2) as its structure is complicated, any malfunction of one of the elements may result in the ladder becoming inoperable; and
(3) the control lever (not shown) generally used in conventional folding ladders for making an angular adjustment thereof is only supported by a single fulcrum. If the control lever is inadvertently touched during operation, the locking member thereof may disengage and slip off, which may result in the collapse of the ladder, and may even endanger the life of the user.